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Unleash the power of MkDocs with macros and variables

Project description

mkdocs-macros-plugin: Unleash the power of MkDocs with variables and macros

Overview

This is a fork of mkdocs-macros-plugin at fralau/mkdocs_macros_plugin for changes in mkdocs version 1.0.2. Will be removed as soon as mkdocs-macros-plugin gets fixed.

mkdocs-macros-plugin is a plugin to make it easier for the contributors to a MkDocs website to make richer and more beautiful pages, by using variables and calls to macros in the markdown code.

Regular variables can be defined in three ways:

  1. global (for contributors): in the mkdocs.yml file, under the 'extra' heading
  2. global (for programmers): in a main.py file (Python), by adding them to a dictionary
  3. local (for contributors): in the markdown file, with a {%set variable = value %} statement

Similarly programmers can define macros, as Python functions in the main.py file, which the users will then be able to use without much difficulty inside of the Python code.

With these two tools, you could write e.g.:

The unit price of product A is {{ unit_price }} EUR.
Taking the standard discount into account,
the sale price of 50 units is {{ price(unit_price, 50) }} EUR.

Which could translate into:

The unit price of product A is 10.00 EUR.
Taking the standard discount into account,
the sale price of 50 units is 450.00 EUR.

The result of a macro can be HTML code: this makes macros especially useful to make custom extensions to the syntax of markdown.

In reality, it is possible to use the full range of facilities of Jinja2 templates.

Context and purpose

Sources of inspiration

mkdocs-markdownextradata (rosscdh)

The idea for that extension came to me after I saw the excellent plugin mkdocs-markdownextradata created by rosscdh, which takes metadata data from the mkdocs.yml file, and allows you to insert them with double curly brackets:

The price of the item is {{price}}.

His concept of using the jinja2 templating engine for that purpose was simple and beautiful: all it took for this plugin was a few lines of code.

jinja2: variables can also be Python callables

And then I discovered that the creators of jinja2, in their great wisdom (thanks also to them!), had decided to support any kind of Python variables, including the callables, typically functions, e.g.:

The price of the item is {{calculate(2, 7.4)}}.

They did not think it was worth more a few words, but it was a diamond in plain sight.

Oh yeah? So let's support them also in the markdown pages of MkDocs!

Macros in Wiki engines

The idea of using 'macros' to speed up the process of writing web pages is in fact rather old.

Most wiki engines, which also rely on some markup language, had the same problems of enriching the presentation of the pages, at the turn of the year 2000. In response, they often implemented macros in one form or another (in mediawiki, they were confusingly called templates). And in many cases, these wiki engines relied on the double-curly-braces syntax.

After all, a static website generator can be defined as a wiki whose online editing features have been removed, to make it "wiki-wikier"!

Use Case: Overcoming the Intrinsic Limitations of Markdown Syntax

MkDocs is a powerful and simple tool for generating websites. Pages are based on markdown, which is simple by design. The downside is that the expressiveness of markdown is necessarily limited.

What do you do if you want to enrich your web with new features like buttons, fancy images, etc. without messing up with templates?

Solution 1: Markdown extensions

In order to express more things with it, the standard recourse is to extend markdown through standard markdown extensions. Adding extensions is straightforward, as they can be directly activated through the mkdocs.ymlconfiguration file of the website e.g.:

markdown_extensions:
    - footnotes

(If they are non-standard, you just have to install them first on your machine.)

The problem is, however, that there will always be something specific you will want to do, for which there is no markdown extension available. Or the extension will be too complicated, or not quite what you wanted.

Furthermore, the are limitations to the number of possible extensions, because extending the grammar of markdown is always a little tricky and can create incompabilities with the standard syntax or other extensions.

Solution 2: Custom HTML Code

If don't have an extension, the standard recourse is to write some pure HTML within your markdown, which may also contain some css code (especially if you are using css that is specific to your theme or website), e.g.:

Here is my code:

<a class='button' href="http:your.website.com/page">Try this</a>

The combination of HTML and css works well and can solve a wide range of issues.

But it will soon become tedious, if you have to type the same code again and again with some variations; and if you want to change something to the call (typically the css class), you will then have to manually change all instances of that code, with all the related risks. This solution doesn't scale.

Solution 3: Enter Macros

What if you had a macro instead, that would allow you to write the above HTML as:

{{button('Try this', 'http:your.website.com/page')}}

... that call was translated into the proper HTML?

That would be something you could teach to a person who can already write markdown, without the need for them to get involved in any css or HTML!

And, what's more, you could easily (as a programmer) write your own new macro in Python, whenever you needed one?

A macro is, simply stated, a Python function that takes a few arguments and returns a string. It could contain all the logic you want; it could be as simple as the example above, or as sophisticated as making a query from a database and formatting the results as markdown.

All of this becomes possible, thanks to mkdocs-macros-plugin!

Installation

Prerequisites

Only tested with

  • Python version > 3.7.0
  • MkDocs version > 1.0.2

Procedure

To install the package, execute:

pip install mkdocs-macros-plugin 

Declare the plugin in the the file mkdocs.yml:

plugins:
    - search
    - macros

Note: If you have no plugins entry in your config file yet, you should also add the search plugin. If no plugins entry is set, MkDocs enables search by default; but if you use it, then you have to declare it explicitly.

How to use it

Defining variables in the configuration file

To easily and quickly define custom variables, declare them in you mkdocs.yml file:

extra:
    price: 12.50
    company:
        name: Acme
        address: ....
        website: www.acme.com

In your markdown file:

The price of the product is {{ price }}.

See [more information on the website]({{ company.website }}).

See <a href="{{ company.website }}">more information on the website</a>.

Defining variables in the markdown page

If you need a variable that is local to a markdown page, you can use a standard Jinja2 declaration, e.g.:

{% set acme = 'Acme Company Ltd' %}

Please buy the great products from {{ acme }}!

In fact, you can do all the fancy footwork you want with Jinja2! Only remember that you don't need to define any header, footer or navigation, as this is already taken care of by MkDocs.

Defining variables and macros in Python code

Location of the module

Python code must go into a main.py file in the main website's directory (beside the mkdocs.yml file).

In can also be a package (i.e. a main directory), as long as the declare_variables function is accessible.

If you wish, you can change the name of that module by adding a python_module parameter to the mkdocs.yml file (no need to add the .py suffix):

python_module: source_code

Content of the module

As a first step, you need declare a hook function called declare_variables, with two arguments:

  • variables: the dictionary that will contain your variables.
  • macro: a decorator function that you can use to declare a Python function as a Jinja2 callable ('macro' for MkDocs).

The example should be self-explanatory:

def declare_variables(variables, macro):
    """
    This is the hook for the functions

    - variables: the dictionary that contains the variables
    - macro: a decorator function, to declare a macro.
    """

    variables['baz'] = "John Doe"

    @macro
    def bar(x):
        return (2.3 * x) + 7



    # If you wish, you can  declare a macro with a different name:
    def f(x):
        return x * x

    macro(f, 'barbaz')

    # or to export some predefined function
    import math
    macro(math.floor) # will be exported as 'floor'

Your registration of variables or macros for MkDocs should be done inside that hook function. On the other hand, nothing prevents you from making imports or declarations outside of this function.

Note: You can export a wide range of objects, and their attributes remain accessible (see more information)

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